The quest is a direct continuation of "Truly Mouthwatering." Without completing it, you won't be able to start this quest, so I recommend taking a look at the article about the first part first.

How to Start the Quest "Still Mouthwatering" in Genshin Impact

Access to this quest is unlocked immediately after completing the first one. Henry will ask you to gather 7 Mysterious Cores - this is the most challenging task of the quest (because they are not marked on the map in any way), and we will now explain how to find them.

Location of All Mysterious Cores on the Map

The locations of all the puzzles are marked on the photo.

How to Solve Puzzles with Mysterious Cores?

First Puzzle with Mysterious Core

On the southern side of Elinas, you will find the first puzzle - a floating spherical device and an Ousia block nearby. The solution is as follows: pick up the block and hit the tin can - it doesn't matter where you hit it, it will activate in any case. A group of mechanical enemies will spawn nearby, which you need to defeat (keep in mind that enemies will keep spawning regardless of the puzzle number). Now pick up the Pneuma block and repeat the same procedure. Another small battle, then the Pneuma block. Congratulations - you now have the first component and some primogems in your hands. 

For triggering the launch, attacks from characters inherently possessing Pneumosia (pneuma) will work, rather than characters artificially endowed with it. Whether to bother with it or not is up to you.

Second Puzzle with Mysterious Core

Now head south of Mount Atonaki. The principle is the same - shoot and defeat enemies multiple times. Difficulty might arise in finding one of the blocks, the Pneuma block (since it's located at a distance), so the photo is attached.

Third Puzzle with Mysterious Core

You will encounter a levitating mechanism while strolling along the eastern coast of Elinas. The solution is the same as before. 

Fourth Puzzle with Mysterious Core

The next one is located near the Pale Forgotten Glory domain, at the bottom of the sea, like the others. Finding the blocks can be particularly engaging: the Ousia is hidden (in the screenshot, it's already destroyed) in a stone that can be broken using the temporary skill of the luminous crab. The Pneuma, on the other hand, is retrieved from a destroyed bullet, which you can do by reflecting the shot fired by the cannon using the aforementioned skill (this skill is also useful for dealing with the two waves of enemies that appear during the launch).

Fifth Puzzle with Mysterious Core

Located in the Sal Terrae sea area. You can find the Pneuma by interacting with the glowing echinus - interact with it and follow the direction of the blue circles. 

Retrieve the block, both of them. For the Ousia, there's a small caveat: ignore the first two closest circles and immediately swim towards the farthest one (otherwise, you risk encountering not very friendly underwater creatures).

Sixth Puzzle with Mysterious Core

In the same vast Sal Terrae area, but a bit to the north. The locations of the blocks are indicated in the photo below.

Seventh Puzzle with Mysterious Core

Head south to the Thalat underwater valley. 

Unfortunately, if you had previously wandered around the location and committed a genocide of algae (just like me, welcome to the club of unlucky gentlemen), the Ousia block that's hidden in the vegetation will be inaccessible to you - it won't be there, because, apparently, the game doesn't provide a respawn, or it conveniently bugs out at this stage of the quest. You'll have to rely on a character with the respective element (Lynette, Hydro Traveler).

Both cores are encased in peculiar cells, so you'll need to steal the glowing skate's blades and sever the green shackles. Cut them at an angle to hit all the spheres at once; individually, it won't work, as they regenerate too quickly.

How to Complete the Quest "Still Mouthwatering" and Get the Achievement "Maddening Taste" in Genshin Impact

Next, you need to hand the gathered metallic junk to Henry. His location is marked on the map in case you forgot from the previous time.

In general, the remaining part of the quest is mostly dialogue, so let's move on to the most rewarding part - the rewards. You'll receive 350 Adventure EXP, 30,000 Mora, ore, Hero's Wit books, two chests with 20 Primogems each, and the secret achievement "Maddening Taste" for confiscating the chicken lying in the sand.

Hope the guide was useful in fulfilling its purpose!